1. Technical Field
The present invention relates to an electronic structure, and associated method of fabrication, for coupling a heat spreader above a chip to a chip carrier below the chip.
2. Related Art
A chip on a chip carrier may have a heat spreader on a top surface of the chip, such that the heat spreader is directly coupled to the chip carrier by an adhesive material that encapsulates the chip. If the heat spreader and the chip carrier have about a same coefficient of thermal expansion (CTE), then the adhesive material helps keep the chip carrier-chip-heat spreader structure approximately flat during thermal cycling. Nonetheless, cracking resulting from thermal cycling has been observed to occur at the surface of the chip carrier where a bounding surface of the adhesive material contacts the chip carrier. The cracking can propagate into the chip carrier and damage circuit lines within the chip carrier.
A method and structure is needed for preventing said damage to said circuit lines within the chip carrier.
The present invention provides a method for forming an electronic structure, comprising the steps of:
providing a substrate, a chip on a surface of the substrate and coupled to the substrate, and a thermally conductive member;
forming a fillet of at least one adhesive material on the chip and around a periphery of the chip and placing the thermally conductive member on a portion of the fillet and over a top surface of the chip, wherein the at least one adhesive material is uncured, wherein the fillet couples the thermally conductive member to the substrate, and wherein an outer surface of the fillet meets the surface of the substrate at a contact curve and makes an average contact angle xcex81AVE with the surface of the substrate; and
curing the at least one adhesive material after which the outer surface of the fillet makes an average contact angle xcex82AVE with the surface of the substrate such that xcex82AVE does not exceed about 25 degrees.
The present invention provides an electronic structure, comprising:
a substrate;
a chip on a surface of the substrate and coupled to the substrate;
a fillet of at least one adhesive material on the chip and around a periphery of the chip, wherein an outer surface of the fillet meets the surface of the substrate at a contact curve and makes an average contact angle xcex8AVE with the surface of the substrate, and wherein xcex8AVE does not exceed about 25 degrees; and
a thermally conductive member on a portion of the fillet and over a top surface of the chip, wherein the fillet couples the thermally conductive member to the substrate.
The present invention method and structure for coupling a heat spreader above a chip to a chip carrier below the chip in a manner that prevents damage to circuit lines within the chip carrier during thermal cycling operations.